1. Field of the Invention
The present invention relates to the field of steam turbines and, in particular, to the valve apparatus for introduction of steam into the turbine housing.
2. Description of the Prior Art
Steam turbines are normally divided into two (2) generally broad categories, those used for the generation of electric power and those used as general purpose units for driving pumps, compressors and the like. The horsepower output of the turbine is related to the revolutionary speed of the turbine which, in turn, is governed by the thermodynamic properties of the steam introduced into the turbine. Most turbo-electric generator drives operate at either 1800 or 3600 rpm. Inlet steam would usually be in the range of 250 lbs./sq. inch gauge at 0 super heat up to 850 lbs./sq. inch gauge at 900.degree. F. Pressures of 1500, 1800, and 2400 lbs./sq. inch gauge are also common for large turbine generators and some even operate at super critical pressures of 3500 and 5000 lbs./sq. inch gauge.
The steam turbines normally operate as a single stage, single valve turbine wherein a single governor valve in a steam chest regulates the introduction of the steam into a single stage housing. A second type of steam turbine is a multi-stage single valve turbine in which, again, a single valve regulates the introduction of the steam into a turbine housing in which the turbine blades are arranged in a multi-stage arrangement. The third type of steam turbine is a multi-stage, multi-valve turbine wherein multiple valves regulate the introduction of the steam into the turbine housing wherein the turbine blades are positioned in a multi-stage arrangement.
In all of the above-identified instances, the steam is accumulated in a steam chest immediately prior to introduction into the turbine housing. The introduction is accomplished by means of the valve mechanism which in either the single or multi-valve arrangement normally consists of a poppet-type valve positioned intermediate to the turbine housing and a steam chest which when opened allows the introduction of steam into the turbine housing.
For optimum efficiency, the steam must be introduced at the desired time and under the desired parameters and directed with optimum efficiency on the turbine blades. The steam itself should be free of all solids. Unfortunately, this cannot always be accomplished. As such, certain inefficiencies develop in the steam turbine, one of which is the sticking of the valve stems due to a buildup on the stems of impurities contained in the steam. The sticking of the valve stems not only affects the efficiency of the steam turbine, but also, if gone undetected or uncorrected, can lead to mechanical damage to the turbine and down time and loss of power or use of the turbine.
Applicant has developed a spherical rotary valve system for use in internal combustion engines as evidenced in U.S. Pat. Nos. 4,944,261; 4,953,527; 4,976,232; 4,989,558; 4,989,576 and 5,109,814. Applicant has further refined this spherical rotary valve technology to replace the popper valve in a steam turbine with a spherical rotary valve which eliminates certain inefficiencies which develop with respect to a steam turbine utilizing a poppet valve for introduction of steam into the turbine chamber and further allows greater control of the timing, amount, and direction of steam to the turbine blades.